内蒙古狼山地区早石炭世石英闪长岩U-Pb年龄、地球化学特征及其对古亚洲洋俯冲的指示  

U-Pb age and geochemical characteristics of quartz diorite in Early Carboniferous from Langshan area of Inner Mongolia,and its implication for subduction of Paleo-Asian Ocean

作　　者：田健 滕学建 刘洋[1] 滕飞 郭硕 何鹏[1] 王文龙 TIAN Jian;TENG Xuejian;LIU Yang;TENG Fei;GUO Shuo;HE Peng;WANG Wenglong(Tianjin Center of China Geological Survey,Tianjin 300170,China)

机构地区：[1]中国地质调查局天津地质调查中心,天津300170

出　　处：《地质通报》2020年第7期1035-1045,共11页Geological Bulletin of China

基　　金：中国地质调查局项目《阴山成矿带小狐狸山和雅布赖地区地质矿产调查》(编号:DD20160039)。

摘　　要：内蒙古狼山山脉西侧分布大面积的晚古生代岩浆岩,时代集中在早石炭世—晚二叠世,早石炭世石英闪长岩体出露于潮格温都尔镇西侧。该岩体岩性为石英闪长岩,LA-ICP-MS锆石U-Pb年龄显示,石英闪长岩的206 Pb/238 U年龄加权平均值为337.4±6.6 Ma。岩石暗色矿物以角闪石为主,黑云母次之,富铁,富钠,高钠钾比值,为钙碱性系列;富集大离子亲石元素Rb、K、Pb,不同程度的亏损高场强元素Nb、Ta、P、Ti的特点,稀土元素配分型式为轻稀土元素富集,重稀土元素亏损,弱的负Eu异常,总体反映岩浆弧的地球化学特征。构造环境判别图显示样品点落在大陆边缘弧范围,岩石地球化学特征表明狼山地区早石炭世处于大陆边缘弧构造背景,古亚洲洋石炭纪存在向南俯冲。对比北部造山带西乌旗地区的早石炭世石英闪长岩,两者地球化学特征基本相同。因此,早石炭世古亚洲洋发生了双向俯冲,形成了以石英闪长岩为主的岩石类型。The Late Paleozoic magmatites are distributed in the west of Inner Mongolian Langshan Mountain,with the formation concentrated in Early Carboniferous and Late Permian.The quartz diorite body of Early Carboniferous strata are outcropped in the west of Chaogewenduer Town.LA-ICP-MS zircon U-Pb age shows that the 206 Pb/238 U weighted average age of quartz diorite is 337.4±6.6 Ma.The characteristics of quartz diorite exhibit that the amphibole is the main dark mineral,characterized by enrichment in TFeO(TFeO=4.18%~6.95%)and Na 2 O(Na 2 O=3.11%~4.07%),high Na 2 O/K 2 O(Na 2 O/K 2 O 1.27~2.50),being calc alkaline series,enrichment in LILE(K,Rb,Ba),depletion in Nb,Ta,P and Ti,enrichment in LREE,and depletion in HREE as well as negligible Eu anomalies,which reflects the geochemical characteristics of magmatic arc.Th/Yb-Ta/Yb discriminant diagram shows the samples plot in the area of the continental margin arc.The geochemical characteristics of quartz diorite shows that the tectonic setting of Langshan area belonged to the continental margin arc in Early Carboniferous,the existence of the southward subduction of the paleo-Asian Ocean,and that,compared with the Early Carboniferous quartz diorite in Xiwuqi area of the northern orogenic belt,their geochemical characteristics are basically the same.Therefore,the paleo-Asian Ocean underwent bidirectional subduction in Early Carboniferous and formed the rock type dominated by quartz diorite.

关 键 词：内蒙古 狼山地区 早石炭世 石英闪长岩 大陆边缘弧 

分 类 号：P534.45[天文地球—古生物学与地层学] P597.3[天文地球—地质学]